ArticlePlant physiology2014
Novel roles for the polyphenol oxidase enzyme in secondary metabolism and the regulation of cell death in walnut.
Article in Plant physiology, 2014. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 91 papers, 1 of them a synthesis that pooled it.
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Who cites it
91 citing papers in PubMed, 1 synthesis or guideline pooled it, 289 citations in OpenAlex.
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- Effect of ethanol vapor on anti-browning and antioxidant properties of fresh-cut stem lettuce via regulation of reactive oxygen species metabolism.Scientific reports · 2026Article
- The Walnut's Dark Secret: Polyphenol Oxidase and the Enigmatic Pathway to Melanin.International journal of molecular sciences · 2026Review
- Birth and death evolution of polyphenol oxidase (PPO) gene family in Oryza species.Botanical studies · 2026Article
- Classification and metabolomic profiling of walnut pellicle polyphenols using a Pseudotargeted metabolomics approach.Food chemistry: X · 2026Article
- Comparative analysis of enzymatic defence mechanisms in Sapindus mukorossi Gaertn. and Acacia concinna (Willd.) DC. using a Michaelis-Menten kinetic model.Scientific reports · 2026Article
- Combined drought and heat stress intensifies antioxidant responses and gene expression in Persian walnut (Juglans regia L.).BMC plant biology · 2025Article
- Co-expression analysis provides a new strategy for mining key metabolites and genes in response to drought stress in Agropyron mongolicum.Plant molecular biology · 2025Article
- Biochemical Analysis of Recombinant Pea Seed Coat-Specific Polyphenol Oxidase (Journal of agricultural and food chemistry · 2025Article
- Biosynthesized sulfur nanoparticles: a novel strategy to enhance antioxidant secondary metabolites in Lotus arabicus L. callus cultures.BMC plant biology · 2025Article
- Assessment of Potential Toxicity of Hyaluronic Acid-Coated Magnetic Nanoparticles on Maize (Molecules (Basel, Switzerland) · 2025Article
- Combining Abiotic Stresses as a Low-Cost Strategy for Increasing the Phenolic Content in Apple Agro-Industrial By-Products.Antioxidants (Basel, Switzerland) · 2025Article
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- Characterization of two bacterial tyrosinases from the halophilic bacterium Hahella sp. CCB MM4 relevant for phenolic compounds oxidation in wetlands.FEBS open bio · 2024Article
- Virtual Cold Chain Method with Comprehensive Evaluation to Reveal the Effects of Temperature Abuse on Blueberry Quality.Foods (Basel, Switzerland) · 2024Article
- Genome-Wide Association Study of Sweet Potato Storage Root Traits Using GWASpoly, a Gene Dosage-Sensitive Model.International journal of molecular sciences · 2024Article
- Investigating the quality of extraction and quantification of bioactive compounds in berries through liquid chromatography and multivariate curve resolution.Analytical and bioanalytical chemistry · 2024Article
31 more citing papers are in PubMed but not listed here.
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Authors and funding
11 authors at 3 institutions in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
The enzyme polyphenol oxidase (PPO) catalyzes the oxidation of phenolic compounds into highly reactive quinones. Polymerization of PPO-derived quinones causes the postharvest browning of cut or bruised fruit, but the native physiological functions of PPOs in undamaged, intact plant cells are not well understood. Walnut (Juglans regia) produces a rich array of phenolic compounds and possesses a single PPO enzyme, rendering it an ideal model to study PPO. We generated a series of PPO-silenced transgenic walnut lines that display less than 5% of wild-type PPO activity. Strikingly, the PPO-silenced plants developed spontaneous necrotic lesions on their leaves in the absence of pathogen challenge (i.e. a lesion mimic phenotype). To gain a clearer perspective on the potential functions of PPO and its possible connection to cell death, we compared the leaf transcriptomes and metabolomes of wild-type and PPO-silenced plants. Silencing of PPO caused major alterations in the metabolism of phenolic compounds and their derivatives (e.g. coumaric acid and catechin) and in the expression of phenylpropanoid pathway genes. Several observed metabolic changes point to a direct role for PPO in the metabolism of tyrosine and in the biosynthesis of the hydroxycoumarin esculetin in vivo. In addition, PPO-silenced plants displayed massive (9-fold) increases in the tyrosine-derived metabolite tyramine, whose exogenous application elicits cell death in walnut and several other plant species. Overall, these results suggest that PPO plays a novel and fundamental role in secondary metabolism and acts as an indirect regulator of cell death in walnut.
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